The Black Knights' Tango (1.d4 Nf6 2.c4 Nc6!?) is an offbeat but sound defense that has been favored by such players as Joel Benjamin and Alex Yermolinsky. Black immediately takes a lead in development, and will strike back in the center with ...e5 or ...d5. The opening has successfully weathered aggressive attempts at refutation like the Lunge Variation 3.d5 Ne5 4.e4 e6 (4...Nxe4?? 5.Qd4!) 5.f4 Ng6 6.e5 Ne4.
White players often are unfamiliar with the Tango, and commonly fall into the trap below. I have played the opening many times on FICS, and find that about 10% of my opponents have fallen into it. After 3.Nc3 (3.Nf3, the most common move, avoids Black's counter-thrust 3...e5) e5! 4.d5 Ne7 5.e4 Ng6 6.Bd3 Bc5 (see diagram), the blunder 7.Nge2?? is one of White's most popular moves! The database www.365chess.com contains 12 games with 7.Nf3, 11 with 7.a3, and 10 with 7.Nge2?? After 7.Nge2?? Ng4!, striking at the f2 square, White is already lost. For example, (a) 8.Be3 Bxe3 9.fxe3 and now either (1) 9...Nxe3 10.Qd2 Nh4 (or 10...Nxg2+), or (2) 9...Qf6; (b) 8.b4?! Nxf2 9.Qb3?? Nxd3+ 0-1 Collier-Yermolinsky, New York Open 1993; (c) 8.Rf1 (sad, but maybe the best practical try) Nxh2! (better than 8...Qh4 9.Ng3! Nxh2? 10.Rh1! with a weird position where Black's knight is marooned on h2) 9.Rh1 Ng4 10.Rf1 Qh4. White often makes a terrible position even worse with (d) 8.0-0? Qh4!, striking both h2 and f2, as in Kosov-Chiarotto below and many other games. Black wins an exchange and a pawn after the forced 9.h3 Nxf2 10.Rxf2 Qxf2+ 11.Kh1 (not 11.Kh2?? Nh4! winning the house, Seifert (2099)-Llobel Cortel (2198), Litohoto 1999, since White cannot play 12.Qg1 Nf3+). White gave up after a few more moves.
